1. Field of the Invention
The present invention relates to a scroll fluid machine for compressing or expanding or pressure feeding fluid, specifically to a seal configuration of a scroll fluid machine having multistage compression section in which the fluid compressed in the preceding stage compression section is cooled to be compressed in the succeeding stage compression section and a seal element is provided to prevent the leakage of the compressed fluid from the succeeding stage compression section to the preceding stage compression section.
2. Description of the Related Art
It is general in scroll fluid machines that revolving scrolls and stationary scrolls are cooled with cooling air or cooling fluid to remove the heat generated by the compression of the fluid. To attain a compression ratio larger than usual is possible by increasing the number of turns of the scroll. However, there arise problems by increasing the compression ratio than usual that not only the machine becomes large but the life of the bearings and seal elements are shortened due to the high temperature higher than usual owing to the larger compression ratio.
Therefore it becomes necessary to provide a larger cooling device to obtain a larger amount of cold heat for removing the increased heat due to increase compression ratio from the revolving scroll and stationary scroll. In a scroll fluid machine, the fluid is taken in from the peripheral part of the end plate of the revolving scroll, the compression space into which the fluid is taken in is reduced toward the center to compress the fluid, and the compressed fluid is discharged from the discharge port located in the center part. High level technique is necessary to efficiently cool the center part.
For this reason, a multistage compression type scroll machine was demanded which has two stages of compression sections, the compressed fluid discharged from the preceding stage being passed through the cooler to be introduced to the succeeding stage to be again compressed. The multistage compression type scroll machine can compress fluid to a desired high compression ratio without raising the temperature of the constituent parts of the scroll fluid machine higher than usual by restraining the temperature of the compressed fluid in the preceding stage to the temperature the constituent parts allow, cooling the compressed fluid compressed in the preceding stage compression section, and then again compressing the compressed and cooled fluid if the succeeding stage compression section.
A multistage compression type scroll machine which has two stages of compression sections and in which the compressed fluid from the preceding stage is cooled by passing through a cooler and then introduced to the succeeding stage to be again compressed is disclosed in Japanese Unexamined Patent Publication 54-59608.
The conventional art includes, however, the problem as described below. This will be explained with reference to FIGS. 10 to 12. The discharge port 2e in the vicinity of the final compression chamber of the preceding stage compression section and the suction port 2f, which communicate with the space into which the fluid is taken in, of the succeeding stage compression section are connected with a piping by the medium of a cooler not shown in the drawing, the connection constituting an intermediate passage.
Now, after the compression space S3 of the preceding stage compression section communicates with the discharge port 2e of the preceding stage compression section, the compression space S6 and T6 of the succeeding stage compression section become communicated with the compression space S5 of the preceding stage compression section, as shown in FIG. 10. The fluid taken into the compression space S6 is compressed by the rotation of the revolving scroll lap 10b to the compression space S8, and the fluid taken into the compression space T6 is compressed to the compression space T8. Therefore, the pressure in the space S8 is higher than that in the space S6, and the pressure in the space T8 is higher than that in the space T6.
As can be seen in FIG. 11(a), FIG. 11(b), and FIG. 12, which show respectively Axe2x80x94A section, Bxe2x80x94B section, and Cxe2x80x94C section in FIG. 10, a tip seal 53 is received in the groove 41 formed in the tip of the revolving scroll lap 10b and in the groove 40 formed in the tip of the stationary scroll lap 9c respectively. As the tip seal 53 is shaped narrower in width than that of the groove 40 and 41, the tip seals 53, 53 receive the pressure of the compressed fluid of each compression space to be pushed against the mirror face each mating scroll and at the same time to be pushed against the wall each groove toward lower pressure side.
Accordingly, the passage 30 and 31 communicating with the compression space T6 are formed as shown in FIG. 11(a), and the leakage to the lower pressure space T6 is possible.
The passage 32 and 51 communicating with the compression space S8 are formed as shown in FIG. 11(b), and the leakage to the lower pressure space S6 is possible.
The tip seal is pushed against the groove wall toward lower pressure side. However, the side face of the tip seal and the groove face can not be brought to absolute contact with each other because of the imperfect flatness of the faces. Accordingly, the leakage of high pressure fluid in the direction of arrow 76 to the gap 80 between the tip seal 14 and 53 is possible as shown in FIG. 12(a) which shows Cxe2x80x94C section in FIG. 10.
There is a gap between the bottom of the groove formed in the tip of the revolving scroll lap and the tip seal 53, so the leakage of the fluid is possible from higher pressure side to lower pressure side. This means that, as a gap exists between the end face 41a of the groove 41 and the end face 53a of the tip seal 53 at the end part 10d of the revolving scroll lap 53, the leakage of the compressed fluid in the direction of arrow 78 is possible, and also the leakage as shown by arrow 77 is possible from the passage 51.
Therefore, as shown in FIG. 10 and FIG. 12(a), the high pressure fluid leaks from the succeeding stage compression section to the preceding stage compression section through the gap 80 shown by arrow 29 and 76 to be taken into the preceding stage compression section to be compressed again, which causes problems of high temperature and excessive power requirement for compression.
The present invention was made to solve the problem mentioned above, the object is to provide the seal construction of a multi-stage compression type scroll fluid machine for preventing the leakage of high pressure compressed fluid to the preceding stage compression section from the succeeding stage compression section.
To solve the problem mentioned above, the present invention offers a scroll fluid machine with multistage compression section in which the fluid compressed in the preceding stage compression section is further compressed in the succeeding stage compression section characterized in that:
a lap groove is formed spiraling from the vicinity of the discharge port of the compressed fluid of the final stage compression space to the fluid take-in side of the initial stage compression space, in the tip of the lap being formed a tip seal grove to receive a seal element, and a rand is formed between the discharge port at the compression end part of said preceding stage compression section and the suction port of the succeeding stage compression section; and
an intermediate seal element is received in the intermediate groove formed on the surface of said rand which faces the end plate of the mating scroll for preventing the leakage of the compressed fluid from said succeeding stage compression section to said discharge port opening side of said preceding stage compression section.
In the present invention, the scroll lap on the tip of which is located a tip seal which contacts and slide on the mating scroll end plate, is formed spirally from the vicinity of the discharge port of compressed fluid in the final stage compression space toward the take-in side of the initial stage compression section forming lap grooves between said lap and the adjacent lap of the mating scroll; and a rand is formed between the discharge port at the end part of the lap groove of said preceding stage compression section and the suction port at the starting part of the lap groove of said succeeding stage compression section. The compressed fluid discharged from said discharge port is introduced in said succeeding stage compression section from said suction port via an intermediate passage provided with a cooler.
Said rand may be formed in the stationary scroll or in the revolving scroll.
In the tip groove of the lap is received a tip seal which is pushed by fluid pressure against the mirror surface of the mating scroll end plate, so a gap is produced between said mirror face of the mating scroll end plate and the surface of said rand, and said discharge port opening is communicated through said gap with said suction port opening. Therefore, the compressed fluid leaked from space S6, T6, and T8 as shown by arrow 29 and 76 toward said suction port opening of the succeeding stage compression section (the leak passage is explained in FIG. 11, 12) advances toward said discharge port opening of the preceding stage compression section. But, according to the present invention, an intermediate seal element is provided on the rand between said suction port opening and said discharge opening, so the leakage of the compressed fluid toward the discharge port opening side is prevented.
The seal element consists of a tip seal received in the tip groove formed in the spiral lap and an intermediate seal element received in the grove formed in the rand between the discharge port opening and the suction port opening.
As shown in FIG. 2 for example, the seal element 26 (tip seal) seals to partition the lap groove in the succeeding stage compression section, a seal element 14 (tip seal) seals to partition the lap groove in the preceding stage compression section, and an intermediate seal element 25 seals the gap between the rand and the mating scroll end plate. The seal element 26 is the extension of the seal element 14.
It is suitable to form the intermediate seal element as circular seal element partitioning the succeeding stage compression section circularly.
In this case, as shown in FIG. 6 for example, the intermediate seal element is formed as a closed, single circular seal, part of which contributes as the intermediate seal on the rand between the suction and discharge port opening. As the seal element surrounds completely the succeeding stage compression section as a single seal element, effective seal between the succeeding stage compression section and the preceding stage compression section is performed.
It is also suitable that the seal element consists of a first seal element which extends spirally from the fluid take-in side of said preceding stage compression section side to the final discharge port side of said succeeding stage compression section and partitions said discharge port opening and said suction port opening at said rand surface in the course of its extension; and a second seal element, an end of which contacts the side face of said first seal element at the side opposite to said discharge port opening in the vicinity of said discharge port opening and which extends from the vicinity of said discharge port opening to the vicinity of said discharge port opening, surrounding said succeeding stage compression section to contact the side face of said first seal element at the side opposite to said suction port opening.
It is also suitable that a tip seal groove is formed extending spirally from the fluid take-in side of said initial stage compression section toward the compressed fluid discharge port side of said final stage compression space,
an intermediate groove is formed communicating with said tip seal groove in said rand between said discharge port opening and said suction port opening, a set of seal elements consisting of a plurality of seal elements is received in said intermediate groove and said tip seal groove, said seal set consists of;
a first tip seal which extends from the compressed fluid discharge port side of said final stage compression space toward said initial stage compression space via said intermediate groove,
a second tip seal which extends parallel with said first tip seal from the compressed fluid discharge port side of said final stage compression space to the vicinity of said suction port opening where the second tip seal depart from said first tip seal and contacts said first seal in the vicinity of said discharge port opening, and
a third tip seal which extends in said tip groove parallel with said second tip seal from the vicinity of said suction port opening to partition said succeeding stage compression section circularly and further extends parallel with said first tip seal toward said initial stage compression section side.
With this configuration, as shown in FIG. 8 for example, the third tip seal 68 is located in the outer side of the second tip seal 69 which contacts the side face of the first tip seal 67 in the vicinity of the discharge port opening, so the contact portion of the first tip seal 67 and the second tip seal 69 is covered by the third tip seal. Thus, the sealing between the preceding stage compression section and the succeeding stage compression section is performed by the first seal element and the second seal element completely like the case shown in FIG. 6, and the leakage of the compressed fluid to the preceding stage compression section is effectively prevented.
It is also suitable that a tip seal groove is formed extending spirally from the fluid take-in side of said initial stage compression section toward the compressed fluid discharge port side of said final stage compression space,
an intermediate groove is formed communicating with said tip seal groove in said rand between said discharge port opening and said suction port opening, and
said seal element is a single tip seal received in said tip seal groove and said intermediate groove.
With this configuration of the seal element, the prevention of leakage of the compressed fluid is performed by a single tip seal, and the number of constituent parts is reduced.
In addition, as the tip seal can be inserted into the groove taking the part of the tip seal corresponding to the intermediate groove as the position basis, it is easier to assemble the tip seal into the tip groove. First the intermediate part of the seal element is inserted into the intermediate groove, then the remaining part can be easily inserted along the tip groove toward the center side in one hand and toward the outer periphery side on the other hand.